Facebook may have 500 million friends, an Oscar-nominated film and an Egyptian revolution to its credit. But not everyone embraces the social network, including plenty of Bay Area tech, sports and political luminaries.

That’s right, there’s a category of people who just might be too big — or too busy — to Facebook.

You can’t “friend” Cisco CEO John Chambers on Facebook, or San Jose Mayor Chuck Reed, or Apple mastermind Steve Jobs (though you can find people pretending to be him). You won’t find status updates from San Jose Sharks stars Patrick Marleau or Joe Thornton, or pithy posts from Carl Guardino of the Silicon Valley Leadership Group.

“I don’t use Facebook,” Marleau, the Sharks left wing, said after a practice Thursday. “The people who know me already know my number.” And, he added, “You never know who is going to try to get hold of you, and the reasons behind it.”

Indeed, high-profile people who shun Facebook have a variety of reasons for avoiding the planet’s most popular social networking platform, from privacy concerns to time constraints.

“Facebook isn’t for everyone,” said Zizi Papacharissi, communications professor at the University of Illinois at Chicago, and editor of the book “A Networked Self.” “It’s a technology, and you have to find a place for it in your life. Or maybe there isn’t a place for it in your life.”

Chief executives of publicly traded companies, for example, wouldn’t want to talk business on Facebook, some experts say, for fear of posting something that might get them in trouble with stock market regulators, or even with shareholders.

But some CEOs have “fan” pages with updates and photos posted by their public relations teams. Chambers’ page, for example, which recently featured news that he will deliver Duke University’s next commencement address, states “posts are not from John Chambers himself.” Chambers doesn’t use a personal Facebook account, says John Earnhardt, director of social media at San Jose-based Cisco Systems.

“There’s not a lot of time for him to go on and utilize it,” he said. Case in point: Chambers’ schedule this week included being in Spain for a mobile conference on Wednesday and then back in the Bay Area for dinner with President Barack Obama and other tech bigwigs on Thursday.

Lack of spare time is primarily what keeps Guardino from using Facebook, too. “I’m afraid of being sucked in,” said Guardino, who added that he does have a personal account on Twitter because the super-brief format appeals to his yearning for efficiency.

Even though there are privacy controls on Facebook — confusing and labyrinthine, some would say, but controls nonetheless — many in high-visibility positions don’t want to use the site for fear of spilling too much information about themselves in public. Earlier this month, for example, first lady Michelle Obama said during an interview with the “Today” show that presidential daughters Malia and Sasha are not allowed to use Facebook.

And in a recent Newsweek interview with Oscar-nominated actors, none said they were on Facebook when asked. Actor James Franco said he had been briefly, but quit because he didn’t like the way his different groups of friends got slung together in one big pool.

Social media strategist Jeremiah Owyang of the Altimeter Group, based in San Mateo, said some celebrities are “concerned that social media will dilute their brand” by overexposing them to the public.

Some celebs discover, just as the nonfamous have, that Facebook doesn’t suit them. Thornton, the Sharks center, was on Facebook for about a year, a few years back, and then dropped it. “There’s no use for it for me,” he said in a locker-room interview. “I like to keep in contact with about six people in my life, and that’s about it.”

Of course, you can find a good-sized handful of Bay Area luminaries who use Facebook for personal use, including venture capitalist Heidi Roizen, Apple co-founder Steve Wozniak, Salesforce.com CEO Marc Benioff and Olympic ice-skating champion Kristi Yamaguchi. Not to mention the numerous accounts that pretend to be those of famous people like Jobs or Oracle’s Larry Ellison. (Neither company would comment on the topic of high-profile Facebookers. Nor would Facebook.)

Venture capitalist Roger McNamee said he spends at least an hour a day on Facebook, partly promoting his band, Moonalice, and partly keeping in much more regular touch with his friends than he did before Facebook. “Facebook is the best environment for a well-known person, as you have significant control of every aspect of your profile and communications,” he said, though he acknowledged it takes time to learn those controls.

For some hyper-scheduled executives, Owyang said, Facebook can be a streamlined way to check in with one’s personal circle.

Godfrey Sullivan, CEO of Splunk, a privately held San Francisco information technology company, said he enjoys using Facebook to keep up with friends and family only, no business contacts — so much so that he’d even pay for the service.

If he gets “friend” requests from “characters who you’ve known well from business, you like them, but you don’t need them looking at your vacation pictures,” he simply asks them to join his network on LinkedIn, the business-oriented online network.

“I tend to think of it as a digital family photo album,” he said of Facebook. His two teenage daughters lavish their time on the site, he says, but he has to keep his visits succinct, posting a few pictures and commenting on family updates.

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